Material has been extracted from bodies of liquid for decades, if not centuries. For example, people have collected seaweed and algae from bodies of water, as well as surface contaminants from vats of industrial chemicals and oil spills from oceans.
For the past three decades or so, blue-green algae, such as Aphanizomenon flos aquae (AFA), have been used as a source of various nutritional and health supplements. During this time, AFA has been harvested using conventional techniques and subsequently dried and packed for direct consumption, or encapsulated or put into tablet form as a dietary supplement.
Conventional techniques for extracting material from liquid include using screens to strain the material, e.g., blue-green algae held in suspension, from gravity-driven and/or pumped flows in irrigation canals. Another conventional technique has been to drag “drapers” with screens through a body of water to strain suspended blue-green algae (or oil from a spill) from the water.
Each of these conventional methods is non-selective in extracting material. When used to extract blue-green algae, undesirable biomass is often extracted along with the blue-green algae. Consequently, these methods work well for collecting blue-green algae for consumption only to the extent the blue-green algae is the only, or at least the dominant, biomass in the region of the body of water from which the blue-green algae is being harvested. Usually, however, other algae species or zooplankton are present in the region. Thus, these conventional harvesting techniques often lead to undesirable contaminants in the extracted material. For example, these conventional and non-selective techniques can inadvertently extract fish, such as endangered fish, or fish that quickly decay and contaminate the blue-green algae.